Lifting Operations (VMO Standard - Part 2-5)

Transcription

1 OFFSHORE STANDARD DNV-OS-H205 Lifting Operations (VMO Standard - Part 2-5) APRIL 2014 The electronic pdf version of this document found through is the officially binding version

2 FOREWORD DNV is a global provider of knowledge for managing risk. Today, safe and responsible business conduct is both a license to operate and a competitive advantage. Our core competence is to identify, assess, and advise on risk management. From our leading position in certification, classification, verification, and training, we develop and apply standards and best practices. This helps our customers safely and responsibly improve their business performance. DNV is an independent organisation with dedicated risk professionals in more than 100 countries, with the purpose of safeguarding life, property and the environment. DNV service documents consist of among others the following types of documents: Service Specifications. Procedural requirements. Standards. Technical requirements. Recommended Practices. Guidance. The Standards and Recommended Practices are offered within the following areas: A) Qualification, Quality and Safety Methodology B) Materials Technology C) Structures D) Systems E) Special Facilities F) Pipelines and Risers G) Asset Operation H) Marine Operations J) Cleaner Energy O) Subsea Systems U) Unconventional Oil & Gas Det Norske Veritas AS April 2014 Any comments may be sent by to This service document has been prepared based on available knowledge, technology and/or information at the time of issuance of this document, and is believed to reflect the best of contemporary technology. The use of this document by others than DNV is at the user's sole risk. DNV does not accept any liability or responsibility for loss or damages resulting from any use of this document.

3 CHANGES CURRENT Page 3 CHANGES CURRENT General This document supersedes DNV Rules for Planning and Execution of Marine Operations, (1996/2000) Pt.2 Ch.5. Text affected by the main changes in this edition is highlighted in red colour. However, if the changes involve a whole chapter, section or sub-section, normally only the title will be in red colour. Det Norske Veritas AS, company registration number , has on 27 th November 2013 changed its name to DNV GL AS. For further information, see Any reference in this document to Det Norske Veritas AS or DNV shall therefore also be a reference to DNV GL AS. This is a new document in a series of documents replacing the DNV Rules for Planning and Execution of Marine Operations (1996/2000). Extensive revisions and/or amendments have been made, with the following main changes: Section 2 General Requirements is new, combining new content with some original text from Section 5 of the previous Rules. Lifting of objects weighing less than 50 t has been included, with factors/text updated accordingly. Editorial corrections In addition to the above stated main changes, editorial corrections may have been made.

6 Sec.1 Introduction Page Application General SECTION 1 INTRODUCTION This standard provides specific guidance and recommendations for Engineered onshore, inshore and offshore lifting operations, conducted both in air and sub-sea, see [ ]. Engineered refers to lifts that are planned, designed and performed according to requirements in DNV-OS-H101, i.e. specially prepared and documented Weight limitations (upper or lower bound) are not specified herein, however, requirements in other standards and local/international regulations may be relevant and governing, for objects with lower weights (typically less than 50 tonnes) and for operations involving routine lifts. Routine lifts are considered everyday lifts, without specific supporting documentation; e.g. lifts associated with general cargo carrying or portable units from/to supply vessels, minor erection lifts on construction yards, etc. For such lifts higher safety factors may be applicable to compensate the lack of detailed engineering. However, routine lifts are not covered in this standard Complementary standards DNV offshore standards covering marine operations, i.e. DNV-OS-H101, DNV-OS-H102 and DNV- OS-H201 to DNV-OS-H206, are collectively referred to as the VMO Standard. The VMO Standard supersedes and replaces DNV - Rules for Planning and Execution of Marine Operations. See also Table For sub-sea lifting relevant parts of DNV-OS-H206 shall be considered The sea transportation phase for lifted objects and lifting equipment is covered in DNV-OS-H General recommendations for planning, loads and design of marine operations are given in DNV-OS- H101 and DNV-OS-H Objectives and conditions The objectives of this Standard are stated in DNV-OS-H101, Sec.1A The general conditions for use of this Standard are stated in DNV-OS-H101, Sec. 1 B References Numbering and cross references Table 1-1 defines the numbering system used throughout this standard, in comparison with that adopted in some of the DNV-H series of offshore standards, published to date. See Table The text in this standard includes references to documents listed in Table 1-2. Where referred to, the referenced text shall be considered part of this standard. Table 1-1 Numbering Level Numbering Numbering in some published DNV-H standards Sections 1 Sec. 1, 2, 3 Sub-Sections 1.1 A., B., C.. Paragraphs A 100, A 200, A 300 Items , 102.., 201, 202.., 301, Requirements herein are based on the document revisions listed in Table 1-2; however the latest revision shall normally be applicable, unless otherwise agreed.

8 Sec.1 Introduction Page Should: verbal form used to indicate that among several possibilities one is recommended as particularly suitable, without mentioning or excluding others, or that a certain course of action is preferred but not necessarily required May: verbal form used to indicate a course of action permissible within the limits of the document Definitions Definitions are included in DNV-OS-H101; terms of special importance for this standard are defined below. Bobbin: Sheaves applied to increase the bending diameter of double slings around a pin. May also be used to centralise the load, then normally referred to as load centralising bobbin. Cable laid grommet: Steel ropes arranged into a stranded construction, cabled together, right or left lay, and spliced such that there is no end. Cable laid sling: Steel ropes arranged into a stranded construction, cabled together, right or left lay, with a hand spliced eye in each end. Design factor: Factors to be applied for design of structural elements which include relevant load factors, consequence factors, and local dynamics. Dynamic amplification factor: A factor accounting for the global dynamic effects normally experienced during lifting. The dynamic amplification factor is defined as (Dynamic Load + Static Load)/Static Load. Fibre sling: Slings made of high performance man-made fibres. Grommet: Endless sling. Lifting: The activities necessary to lift or assist a structure by crane(s). Lifting equipment/gear: Temporary installed equipment such as slings, shackles, sheaves, spreader beams or frames, necessary to perform the lift. Lifted object: A structure or parts thereof subjected to lifting. Lift points: The attachment points for slings on the lifted object. Lift point are normally designed as padeyes or trunnions/padears. Padear: Type lift point on a structure, normally consisting of a tubular member and an end-plate, to ensure sling retention. The sling/grommet may be laid around the tubular member such that a shackle is not needed. Padeye: Lift point on a structure consisting of a steel main plate with a matched machined or drilled hole for the shackle pin. The hole may be reinforced by a plate (cheek plate) on each side. Plate shackle: A shackle where the bow is replaced by two steel plates and an extra pin. Rigging arrangement: The complete system, as applicable, of slings, shackles and, spreader beams or frames. Shackle: A structural component composed by a bow and a pin linking e.g. a sling/grommet to a padeye. Single laid sling: Preformed steel wire rope, with hand splices, swaged splices, pressed sockets or resin sockets to form eye terminations at each end. Skew load factor: A factor accounting for the extra loading on slings caused by the effect of inaccurate sling lengths and other uncertainties with respect to force distribution in the rigging arrangement. Sling: A strap used between lift point and crane hook during lifting. The term sling is also used for a steel rope with an eye at each end. Spreader beam/frame loose gear and part of the rigging used to: minimise/eliminate compressive forces imparted into the lifted object reduce the effect of inaccurate sling lengths or to avoid clashes between slings and the lifted object. Trunnion: Another name for padear type lift points. It may also be a type of double padear, i.e. a pin (tubular) supported in the centre with slings/grommets on both sides Symbols and abbreviations The list below defines symbols used in this chapter A: Nominal cross sectional area of all 4 slings. CGBL: Calculated Grommet Breaking Load CoG: Centre of gravity. CSBL: Calculated Sling Breaking Load D: Bending diameter of slings.

10 Sec.2 General requirements Page Planning and documentation General SECTION 2 GENERAL REQUIREMENTS Planning, including the design process, documentation and risk management, for lifting operations shall comply with requirements and philosophies given in DNV-OS-H101, Section 2. The documentation associated with the above shall be commensurate with operational complexity and the experience of those parties involved in any given operation Documentation The general requirements to documentation are given in DNV-OS-H101, Section 2B The lifting operation should be clearly described by drawings, calculations and procedures All applicable input data should be documented A manual covering all relevant aspects of the lifting operation should be prepared, see also DNV-OS- H101, Sec.4G All relevant certificates, test reports, release notes and classification documents for equipment, cranes and vessels involved should be available for review. 2.2 Crane and crane vessel General The crane, crane vessel and all associated equipment should be in good condition, properly manned and fit for performing the intended operations The crane should be equipped with a reliable load monitoring system with an accuracy normally not exceeding 5% of the maximum crane capacity, or 10% of the weight of the lifted object Positioning The crane vessel should be positioned, moored and/or operated on DP according to relevant requirements stated or referred to in DNV-OS-H203. For inshore and weather restricted mooring systems the requirements in DNV-OS-H101, Sec. 6B normally apply Crane vessel certificates The crane vessel shall comply with the requirements in DNV-OS-H101, Sec. 6D Hydrostatic stability data should be available on-board The following vessel certificates should normally be presented in valid condition: certificate of registry certificate of classification safety construction certificate certificate of international load line safety equipment certificate Crane documentation The crane lift capacity for the required lift radius and height shall be properly documented, considering all operational limitations and clearance requirements The following crane certificates should normally be presented: Certificate of classification or maker s certificate. Crane test report issued by a recognised authority.

11 Sec.2 General requirements Page 11 Latest annual survey report. Lift record for preceding operations. Load-radius curves for static and dynamic lifting conditions. Limiting condition, see [ ], for each load-radius curve shall be clearly indicated Safe handling instructions for the crane operation shall be available, in particular alarm settings and handling of alarms shall be properly documented Clearly defined operating parameters shall be presented for the applied load-radius curve(s), to ensure that the crane is suitable, given the design assumptions made. The limiting crane operational condition could normally be expressed by relevant combinations of the following (maximum) parameters: a) DAF b) wind speed c) hoist line angle tolerances relative to crane (both in-line and sideways) d) static heel and trim of crane vessel e) crane tip motions/accelerations due to waves f) motions/accelerations of the vessel where the cargo is lifted from g) wave conditions, e.g. expressed by Hs, Tz and relative wave/vessel direction(s) For lifts by two (2) or more hooks on the same crane boom, total lift capacity of the crane (boom) structure shall be documented. The most unfavourable load distribution between the hooks shall be applied. Requirements to hook load distribution assessments are included in [ ]. Note that the DAF indicted in [ ] are based on the load in each hook. 2.3 Operational aspects General General requirements for operational aspects are given in DNV-OS-H101, Section The operation shall be carried out with due consideration of identified risks and prescribed risk mitigations Control of lift The lifted object shall be adequately controlled in order to avoid any significant and undesirable yawing and/or pendulum motions. See also the requirements for bumpers and guides in [5.1.7]. Control should be ensured by applying an adequate combination of: a detailed step by step lift and handling procedure monitoring and evaluating relative crane tip and hook positions before lift-off tugger lines tag lines bumpers and guides Maximum expected (relative) vertical motions of the crane and lifted object should be properly accounted for - see [ ] and [5.1.7] Rotation (yaw motion) of the lifted object should normally be controllable in both directions during all phases of the lift. See also [ ] The use of tugger lines should be properly planned and designed; design documentation should normally include: layout sketches/drawings attachment point detailing required tension in tugger lines due to vessel motions (to avoid slack and snap loads) and how to maintain it

12 Sec.2 General requirements Page 12 tugger line(s) to crane hook and/or spreader bars if applicable capacity checks of all associated components. In general all components associated with the tugger line arrangement (e.g. wires, winches, winch foundations, sheaves and blocks) should have adequate ultimate structural strength (MBL) to withstand the maximum loads which can be imposed on them by the tugger lines. See also [ ] Clearances All relevant clearances should be determined and thoroughly assessed for all stages of the lift Clearances required during crane vessel operations should be determined on the basis of the expected duration of the operation, the operational procedure (see [2.3.2]), crane functionality, environmental conditions, positioning and fendering systems, back-up systems, configuration lay out, possible tilt of object, etc. Minimum clearances should consider maximum motions of the crane vessel and transport vessel/barge, associated with the environmental design conditions and DP capability/mooring system. Required clearance depends on a number of factors such as size and weight of the lifted object, ability to control the lift (see [2.3.2]), vessel motions, weather conditions, consequence of impact loads etc. The following clearances could be used as guidance for objects lifted offshore: a) The minimum clearance between the lifted object or lifting equipment and the crane boom should normally not be less than 3.0 m. b) For objects to be lifted over, around or between other objects a minimum clearance of 3.0 m is recommended. c) Minimum 5.0 m between lifted object and other structures on the same transport barge, unless specific bumpers/ guides/tugger lines are used for lift off. Clearances for lifts by floating crane vessels onto floating structures (e.g. spars, FPSO s) will need special consideration. It is expected that the clearances for this case will need to be larger than those stated above. The design clearances should be defined with due attention to the maximum expected relative motions of the floating structure and the lifting vessel Clearances between the underside of the lifted object and grillage or seafastening structures on the transport vessel/barge should be evaluated, with due consideration given to relative vertical and possible horizontal motions after lift-off. If these clearances are small, particular attention should be given to avoid damages in case of subsequent impacts. The probability of the barge/vessel impacting with the lifted object after lift-off could be estimated using the methods described in DNV-RP-H103 Section The minimum clearances indicated in DNV-OS-H203, Table 4-2 for moored vessels in weather restricted operations and if applicable, Table 4-3 for mooring lines should be considered. The indicated minimum clearance in ULS/ALS is for possible contact with critical structures/elements such as the crane boom, single critical structural elements, under water buoyant compartments and/or sensitive equipment. Clearances to other elements should normally not be less than 3.0 m in ULS Minimum clearances for DP vessels should be defined according to DNV-OS-H203, Sec.5 C200. Guidance note 1: For short time lifting operations close to fixed platforms, a smaller minimum distance than recommended in DNV- OS-H203 may be considered, given that most of the below listed items are giving favourable effect: a) Records of favourable (small) vessel footprints during similar operations are presented. b) Maximum expected yaw motions of the vessel have been considered in the clearance calculation. c) The operational weather conditions are well within the limiting DP capacity in DP 3 (or 2). d) The crane vessel is operating on the leeward side of the installation. e) Possible motions of the installation are considered.

13 Sec.2 General requirements Page 13 If the first contact in case of lost position will be with critical elements, see [ ] GN, the minimum recommended distance is 10.0 m; for contact with non-critical elements this may be reduced to 5.0 m. Adequate (contingency) fendering could be used to further reduce the recommended minimum distance. Guidance note 2: Clearances around the crane vessel (either moored or dynamically positioned) and any floating platform, FPSO, drilling rig or submersible, shall be determined as special cases based on the station keeping analysis of the floating structure and the lifting vessel. Positioning equipment and procedures shall be defined to maintain the minimum clearances required for each specific operation. The procedures should minimise the durations for which these are required Circumstances that could reduce the available lift height according to load-radius curves shall be thoroughly evaluated. In addition to the clearances mentioned in [ ], such considerations could include: a) Varying tide levels, with due consideration given to combinations of floating and/or bottom fixed units/cranes. b) Recommended (3.0 m in ISO ) minimum distance between travelling block and fixed block not properly included in the crane charts. c) Hoist line angle restrictions for multi hook lifts applying fixed (no slewing) crane booms Sufficient bottom clearance between the crane vessel and the sea bed should be documented for lifting operations in shallow waters. There should be a minimum underkeel clearance of 3 m between crane vessel (including thrusters) and seabed, for an offshore lift after taking account of tidal conditions, vessel motions, increased draft and changes in heel or trim during the lift. Lesser clearance for operations in sheltered waters may be applicable depending on the seabed and environmental conditions, but should not be less than 1 m Lifting Operational criteria such as, wind speed, wave conditions, relative motions, etc., should be established prior to starting the lifting operation. These criteria should be included in the operation manual. Guidance note 1: For vessel to vessel lifts relative vertical motion between crane hook and object should be carefully evaluated before commencement of the lift. Relative motions exceeding 2.0 m is not recommended. See also [ ]. Guidance note 2: Considerations should be given to the effect of wind loading to ensure that such loads will not jeopardise the operation. It is recommended that a limiting wind criterion is clearly expressed General crane operational procedures and limitations, see [ ], shall be considered Connection (and disconnection) of the lifting rigging between object and crane hook shall be planned in detail. The planning should/may include items such as, but not limited to: Safe handling during installation/connection of heavy lifting equipment, e.g. shackles, lift tools and spreader bars/ frames. Easy access and appropriate working environment for riggers. Colour coding of slings/lift points to be connected together in order to avoid mix up. Securing (during sea transportation) for rigging equipment that is pre-connected to the object. See [5.1.8]. Back loading of heavy lifting equipment. Lift point detailed design, see e.g. [ ] Practical use requirements, see [4.1.6] and [4.2.2].

14 Sec.2 General requirements Page 14 For subsea disconnection, see DNV-OS-H The crane hook should be positioned accurately over the centre of gravity of the lifted object prior to commencement of the lift. When lifting from another vessel/barge or from shore by crane vessels, possible restraint loads between crane vessel and lifted object should be relieved by slackening mooring lines as much as possible and restricted use of thrusters Ballasting of transportation vessel/barge prior to or during lifting in order to obtain simultaneous lift off at all support points should be considered If counterweights are to be used to adjust the centre of gravity during lifting, such weights should be securely fastened to the lifted object Eccentric and/or none symmetric hook loading should be within acceptable limits. E.g. objects with a CoG distant from the central axis of lift (single hook lifts) will lead to considerable differences in sling angles and eccentric hook loading. It should be documented that the subsequent moment will not overload the hook or blocks, or make rotation of the hook impossible Where shimming arrangements between support structure/grillage and the object are used, shims should be adequately secured to one of the surfaces. Securing to grillage is preferable. If securing has not been properly done a check-point and procedure for removal of shimming plates (that may be stuck under the object) should be included. Removal of shims should preferably be performed immediately after lift-off Monitoring of lifting operations The following parameters should normally be monitored manually/visually or by monitoring systems if needed to obtain sufficient accuracy and/or to ensure adequate response time: hook load(s) crane radius crane slew angle crane boom angle crane block elevation environmental conditions tilt of lifted object, especially for multi-hook lifts relative motions of lifted object position and orientation clearances hoisting velocity Cutting of seafastening The cutting procedure should be such that no vertical restraint will be present during lift off. Vertical cutting of seafastening with a flame cutter may, due to the coarse cut, result in restraining effects. It is recommended that the cut is performed at an angle of degrees minimum (to the vertical) or that each piece is removed using two parallel cuts Rotational restraint, at single support points, e.g. module footings, shall be avoided It should be thoroughly verified (by dedicated personnel) that the cutting is complete before the final go-ahead for lifting is given.

15 Sec.2 General requirements Page 15 It should also be ensured that the crane operator obtain up-to-date load information to be able to stop lift during liftoff phase, in case seafastening not completely cut off Cutlines should be marked on the seafastening in advance. Guidance note 1: Cut lines to be decided with due consideration to avoid damage to the structure and its surface protection. Guidance note 2: To avoid damaging the barge deck and provide for safe and easy handling, considerations should be made to avoid large pieces of loose seafastening debris. Seafastening of large loose seafastening or grillage debris after lift-off should be considered.

16 Sec.3 Loads Page 16 SECTION 3 LOADS 3.1 Basic loads Weight and centre of gravity The object weight (W) as lifted should be the characteristic weight defined in DNV-OS-H102, Sec. 3C Inaccuracies in CoG position should be considered according to the principles in DNV-OS-H102, Sec. 3C 200. Guidance note 1: Geometry changes due to CoG uncertainties may for unconventional rigging arrangements (e.g. for two- or one sling riggings) influence the design loads (e.g. out-of-plane loads on lift points). The effect of geometry changes shall in these cases also be considered. Guidance note 2: To simplify the design and procurement of lifting equipment, lifting points etc. a sling load inaccuracy factor, based on the weight inaccuracy and CoG envelope study are often used; the assumptions used to derive this factor must be confirmed Weight of rigging The weight of rigging (W rig ) is the total weight of the rigging arrangement, i.e. equipment such as shackles, slings, spreader bars or frames, etc Hook, block and hoist line weights do not need to be considered as a part of W rig. This is most relevant for cranes with several possible rigging configurations typically for onshore crawler cranes W rig should be included in the applied crane load, but does not need to be considered for elements below each part of the rigging Special loads When appropriate, allowances for special loads (SPL) should be made. Special loads may include tugger line loads, guide loads, wind loads, hydrodynamic and hydrostatic loads, etc. 3.2 Dynamic loads Dynamic effects All lifts are exposed to dynamic effects due to variation in hoisting speeds, crane and vessel motions, cargo barge movements, object movements etc The effect of global dynamics will be significantly influenced by parameters such as: environmental conditions rigging arrangement type of crane vessel stiffness of crane-boom and lifting appliances type of cargo vessel weight of lifted object lifting procedure whether the lift takes place in air, in water or through both. Global dynamic loads should be calculated with due consideration given to these and other parameters, where identified and as applicable. See also [3.2.2] Dynamic effects during lifting onto a floating offshore structure or vessel should be specially considered. See DNV-RP-H102, Section for guidelines For lifts through water special investigations should be made in each case, taking proper account of the

17 Sec.3 Loads Page 17 hydrostatic and hydrodynamic effects, during all critical phases of the lift, see DNV-OS-H206 and DNV-RP- H103. For lifting in water, additional local dynamic effects may govern the design of lifting equipment elements. Such effect could be local sling dynamics due to motion of the object initiated by waves Dynamic amplification factor The global dynamic load effects may be accounted for by using a dynamic amplification factor (DAF) The DAF should for major offshore lifts be established on the basis of a dynamic analysis, considering the effects in [3.2.1] Environmental design conditions applied in the dynamic analysis should be duly reflected in the operations manual, see also DNV-OS-H101, Section 4B In lieu of more refined analyses, the values for DAF given in Table 3-1 may be considered as minimum factors for lifts in air, provided the lifting operation will not take place under adverse conditions. Guidance note 1: The dynamic amplification factors in Table 3-1 are indicated for the following lift types: a) Onshore = Quay and yard crane lifts from/to barge/ship moored along quay. b) Inshore = Lift with crane vessel from/to barge/ship in sheltered waters. c) Offshore = Lift with crane vessel or platform crane from barge/ship (supply vessel) to a fixed platform. See [ ] for lift to a barge/ship. Guidance note 2: The definition of adverse conditions depends on the lift configuration and should normally be defined on the basis of analysis - see [ ]. For offshore lifts with SHL 100 tonnes, the following could be used as general rough guidance: a) Significant swell (i.e. swell with a period and height creating significant crane vessel motions, see e.g. [ ] GN1). b) For lifts not involving ballasting of crane vessels during lift-off, waves with (Hs) > 2-2.5m. c) For lifts involving ballasting of crane vessels during lift-off, waves with (Hs) > 1-1.5m For offshore lifts with SHL < 100 tonnes the following could be used as general guidance: a) Waves with Hs > m (highest value for small SHL). b) Swell/waves that are creating significant motions of the crane vessel. For lifts from small vessels, say with length less than 80m, lesser wave limits should be considered. Guidance note 3: For offshore lifting from deck of SSCV s to a fixed platform, the DAF for inshore lifts in Table 3-1 may normally be used. Also for lifts from own deck with mono hull crane vessels (e.g. for the lifting in air phase of subsea lifts) the inshore factors may be considered applicable for offshore lifts. Note that the DAF should not be taken less than (1.5a + g)/g, where a is the maximum expected/calculated crane tip acceleration due to crane vessel motions in the limiting wave conditions for the lift. Normally a rough estimate of a based on maximum crane tip vertical movement and associated period will suffice to document this requirement.

18 Sec.3 Loads Page 18 Table 3-1 Dynamic Amplification Factors 1) SHL (Static Hook Load) DAF Onshore DAF Inshore DAF Offshore 3.3 Skew loads General 3 2) 100 t t t t > 2500 t ) See Guidance Notes in [ ]. 2) For objects weighing less than 3 tonnes it is recommended to assume an object weight of 3 tonnes and use this throughout the calculations. 3) See [ ] for recommendations to moving cranes onshore Skew loads are additional loading caused by equipment / fabrication tolerances and other uncertainties with respect to asymmetry and associated force distribution in the rigging arrangement. Effects that may cause skew loads are: sling length inaccuracies fabrication tolerances of lift points deflections of lifted object crane hook geometry multi hook lifting doubled slings difference in sling elongations The lifting procedure shall be carefully evaluated for the potential occurrence of skew load effects, other than those mentioned [ ] GN For rigging configurations involving slings from more than 4 lift points converging on a single hook, skew load effects shall be calculated on a case by case basis Skew load effects shall be considered as outlined in the sub-sections below Sling tolerance effects The effects of sling length tolerances are dependent on the fabrication tolerance of slings and lift points, the rigging geometry, sling characteristics and the utilisation of the slings. The effects may be accounted for by a factor SKL sl. In general SKL sl should be calculated for each lift rigging, however for some typical rigging configurations, the standard SKL sl indicated in [ ], [ ], [ ] or [ ] may be applied. Note that the indicated assumptions should be fulfilled. SKL sl for 4 point symmetric lift riggings may also be calculated in accordance with App.A. App.A includes also some background for the SKL sl factors in this sub-section The SKL sl should always be calculated in the following cases: The slings or lift points have excessive fabrication tolerances. The rigging has an unusual geometry, e.g. small sling opening angles, more than 4 slings and/or no symmetry. See also GN. Not any of the standard SKLsl indicated in [ ], [ ], [ ] or [ ] are applicable For statically determinate rigging arrangements (with or without spreader bar) with typical geometry and sling lengths within tolerances of ± 0.5% of their nominal length, a SKL sl of 1.0 may be applied. The effect of tolerances on rigging geometry and sling load distribution should otherwise be considered.

19 Sec.3 Loads Page 19 By typical geometry, it is meant that all slings (i.e. 2 or 3 for statically determinate configurations) carry a significant part of the load and that the angle(s) between any slings is (are) more than 30 degrees. For 3 and 4 sling arrangements, it is normally assumed that the sling angles are between 45 and 70 degrees with the horizontal For four points lifting with floating spreader bars a SKL sl of 1.1 is acceptable, on the assumption that the following conditions are fulfilled: a) An approximately symmetric rigging geometry is utilised. b) The sling lengths are within ± 0.5% of their nominal length. c) The calculated axial load in the spreader bar is at least 15% of the sling load. Guidance note 1: Floating spreader bars, as defined in this standard, are used between two slings in a conventional 4 sling rigging. The floating spreader bars are connected to only two slings in each end. The four slings (two each end) and the spreader bar will form one plane. Guidance note 2: If the stated conditions are not met the SKL sl should normally be found by calculation. However, generally if the length tolerance is stricter than stated the minimum axial load requirement in the spreader bars could be relaxed For statically indeterminate 4 point lifts using cable laid slings or grommets, a SKL sl of 1.25 is normally acceptable, subject to the following conditions: a) The total deviation in length between both diagonals is maximum 0.5% of the nominal length. Note that the manufacturing tolerance needed to satisfy this requirement is quite strict, see [4.1.7] for guidance. See also [ ] GN. b) Sling/grommet elastic modulus E MPa, see also [ ] and App.A. c) The applied slings/grommets have no significant deviations in characteristics (construction, dimension and condition/age/earlier use). d) An approximately symmetric rigging geometry is applied and the slings angles (θ) are maximum 60 degrees with the horizontal. e) The sling/grommet DF is 5.0. DF = MBL / (DHL /4/sinθ), For MBL see [4.1.3] and for DHL see [3.4.2]. If the stated conditions are not met the SKL sl should normally be found by calculation. However, if the length tolerance is stricter than stated, the maximum safety factor and sling angle requirements could be relaxed For statically indeterminate 4 points lifts using wire rope slings or grommets, the SKL sl could be selected according to Table 3-2. Table 3-2 SKL sl for Wire Rope Slings & Grommets SKL Associated diagonal load Distribution Assumptions as defined in [ ] valid (Yes) or modified as indicated below. a) b) c) d) e) /8 3/8 Max. 0.3% E MPa Yes Yes (60 deg.) DF /3 1/3 Max. 0.3% Ang. 70 deg. DF /4 1/4 Yes (0.5%) Yes (60 deg.) DF /5 1/5 Yes (0.5%) Ang. 70 deg. DF 5.6 In order to ensure maximum 0.3% deviation on the diagonals the sling length tolerance needs to be set to +/- 0.15% for slings that are not interchangeable and the lift point fabrication tolerances have to be insignificant. Hence, symmetric (preferably double symmetric) interchangeable rigging is recommended.

20 Sec.3 Loads Page Deflections of object It is normally acceptable to assume that the lifted object has infinite stiffness for the purpose of calculating nominal sling loads and skew load effects; this in most cases will be conservative. However, see [ ]. Deflections of the lifted object could also reduce the SKL sl effects significantly and could be considered whenever found relevant. Note also that the SKL factors in [ ] and [ ] have been calculated considering some object deflection. See also App.A For some lifts with a statically indeterminate rigging system, object deflections could influence the sling load distribution considerably. In these cases it is normally required to carry out structural calculations, with due consideration given to the stiffness of both rigging and lifted object. Typical examples include: Slender objects e.g. spool pieces. Asymmetrically loaded objects with limited torsional stiffness, e.g. non-clad frames or modules and flat skid-type pancakes. Lifts involving more than 4 lift points. All possible combinations of maximum and minimum sling lengths should be included in the model, e.g. by applying temperature elements, in order to find the skew load effects Crane hook geometry The crane hook geometry will influence the theoretical sling angles, lengths and loads. This should be considered The minimum hook prong radius in way of the slings should be included in the hook technical documentation Two (2) prong or asymmetric four (4) prong hooks may reduce the skew load in four (4) sling lifts as the hook may rotate. This may be considered in skew load calculations. A rotation of these hooks will in a horizontal projection reduce the length of one diagonal by that the sling-hook-sling projected line is getting more close to a straight line. The angles in the other sling-hook-sling projected line get greater and this line length hence increase Skew loads for two-hook lifts Skew load effects associated with the use of multi-hook lifts shall be considered, in addition to skew load effects for rigging at each hook. The effect of any CoG position within the defined envelope and the effect of tilt and yaw shall be considered for multi hook lifts. The yaw and tilt effects may result from deviations of the hooks from their ideal, relative positions. The magnitude of this deviation will depend on whether the two cranes are on the same or separate vessels, the vessel's motion response, and the lifting procedure The yaw effect factor SKL y, accounts for increased sling loading due to rotation of the object about a vertical axis; a yaw effect factor of 1.05 is normally sufficient. For lifts with small sling opening angles at the hooks and/or significant wind/tugger line loads a greater yaw effect factor may be applicable A tilt effect factor SKL t, shall be calculated to account for the increased sling loading caused by rotation of the object about a horizontal axis and the effect of out-of-plumb hoist lines. The tilt effect factor should be based on possible tilt caused by maximum hook height tolerances and hoist line deviations from the vertical. For lifting with crane vessels the tilt effect factor may normally be calculated for a tilt of 3 when the hooks (cranes) are on the same vessel and for a tilt of 5 when the cranes are on separate vessels (hoist line out-of-plumb included). Alternatively a maximum possible deviation in hook heights could be defined/documented/controlled and SKL t

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